test(bf-3oy5): fix mock setup for SemanticNarrativePanel tests

The vi.mock() callback was capturing mockManagerInstance at module
load time when it was undefined. Fixed by:

1. Changing mock to vi.fn() without return value
2. Adding mockReturnValue(mockManagerInstance) in beforeEach

This ensures the mock returns the properly configured instance when
getSemanticNarrativeManager() is called during panel construction.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/tui/components/SemanticNarrativePanel.test.ts

@@ -75,7 +75,7 @@ class MockSemanticNarrativeManager {
 let mockManagerInstance: MockSemanticNarrativeManager;
 
 vi.mock('../../semanticNarrative.js', () => ({
-  getSemanticNarrativeManager: vi.fn(() => mockManagerInstance),
+  getSemanticNarrativeManager: vi.fn(),
 }));
 
 // Import after mocking
@@ -203,6 +203,9 @@ describe('SemanticNarrativePanel', () => {
     mockManagerInstance.onUpdate = vi.fn(() => () => {});
     mockManagerInstance.clear = vi.fn();
 
+    // Update the mock to return the new instance
+    (getSemanticNarrativeManager as Mock).mockReturnValue(mockManagerInstance);
+
     mockScreen = createMockScreen();
     onSelectCallback = vi.fn();